Adaptive RFID devices

Abstract

Techniques for RFID communication adaptive to an environment are provided. An RFID reader includes a processor and a reconfigurable hardware element. The reconfigurable hardware element is reconfigurable by the processor in response to a predetermined condition. Non-volatile memory stores configuration code for the reconfigurable hardware element. In specific embodiments, the predetermined condition can be the presence of a mixed tag population, proximity to an interferer, historical read rates, RF noise level, and reader location, as well as other factors.

1 . An RFID reader comprising: 
 a processor;    at least one antenna;    a switch controlled by the processor; and    at least two receiver channels in a radio frequency front-end section coupled to the at least one antenna and the switch, the at least two receiver channels including: 
 a first receiver channel configured to provide a gain for a received signal of a first predetermined range in strength, the gain being substantially linear over the first predetermined range; and  
 a second receiver channel configured to provide a gain for a received signal of a second predetermined signal range in strength, the gain being substantially linear over the second predetermined range.  
   
     
     
         2 . The RFID reader of  claim 1  wherein the gain of the first receiver channel is relatively higher than the gain of the second receiver channel.  
     
     
         3 . The RFID reader of  claim 2  wherein a maximum in signal strength of the first predetermined range is less than a maximum in signal strength of the second predetermined range.  
     
     
         4 . The RFID reader of  claim 1  wherein a maximum region of the first predetermined range overlaps with a minimum region of the second predetermined range.  
     
     
         5 . The RFID reader of  claim 1  wherein the processor is configured to make a selection of a receiver channel depending on signal strength.  
     
     
         6 . The RFID reader of  claim 5  wherein the selection occurs during a preamble sequence.  
     
     
         7 . The RFID reader of  claim 1  wherein the first predetermined range ranges from about 1 μV to about 1 mV.  
     
     
         8 . The RFID reader of  claim 1  wherein the second predetermined range ranges from about 1 mV to about 100 mV.  
     
     
         9 . The RFID reader of  claim 1  further comprising a mixer to mix a received signal with an intermediate frequency signal.  
     
     
         10 . The RFID reader of  claim 1  further comprising a third receiver channel configured to provide a gain for a received signal of a third predetermined range in strength, the third predetermined range encompassing at least a portion of both the first and second predetermined ranges.  
     
     
         11 . The RFID reader of  claim 1  further comprising at least one of a directional coupling element and an isolator element electrically coupled to the plurality of receiver channels.  
     
     
         12 . The RFID reader of  claim 11  wherein the isolator element is a circulator.  
     
     
         13 . The RFID reader of  claim 1  wherein each of the at least two receiver channels includes a band pass filter.  
     
     
         14 . An RFID reader comprising: 
 a processor;    at least one antenna;    a switch controlled by the processor; and    at least two receiver channels coupled to the at least one antenna and the switch, the at least two receiver channels including: 
 a first receiver channel configured to provide a gain for a received signal of a first predetermined range in strength, the gain being about linear with a root-mean-square deviation of less than 5% over the first predetermined range; and  
 a second receiver channel configured to provide a gain for a received signal of a second predetermined signal range in strength, the gain being about linear with a root-mean-square deviation of less than 5% over the second predetermined range.  
   
     
     
         15 . A method of operating an RFID device, the method comprising: 
 transmitting an interrogation signal;    receiving a backscatter signal;    determining a signal strength of the received backscatter signal;    in response to the determining, selecting a receiver channel from a plurality of receiver channels to reduce inter-modulation distortion, each receiver channel to provide a substantially linear gain over a specified range.    
     
     
         16 . The method of  claim 15  wherein the plurality of receiver channels includes: 
 a first receiver channel configured to provide a gain for a received signal of a first predetermined range in strength; and    a second receiver channel configured to provide lower gain relative to the first receiver channel for a received signal of a second predetermined signal range in strength.    
     
     
         17 . The method of  claim 16  further comprising: 
 disposing a tag within an RF field of at least two readers,    wherein a received signal from the tag is within the second predetermined signal range.    
     
     
         18 . The RFID reader of  claim 16  wherein the first predetermined range ranges from about 1 μV to about 1 mV.  
     
     
         19 . The RFID reader of  claim 16  wherein the second predetermined range ranges from about 1 mV to about 100 mV.  
     
     
         20 . The method of  claim 14  wherein the determining occurs during a preamble signal defined by an RFID protocol.  
     
     
         21 . An RFID reader comprising: 
 a processor;    a transceiver;    at least one antenna coupled to the transceiver;    at least one reconfigurable hardware element, the hardware element reconfigurable by the processor in response to a predetermined condition; and    non-volatile memory storing configuration code for the reconfigurable hardware element.    
     
     
         22 . The reader of  claim 21  wherein the reconfigurable hardware element is a field programmable gate array (FPGA).  
     
     
         23 . The reader of  claim 22  further comprising at least one analog-to-digital converter and at least one digital-to-analog converter.  
     
     
         24 . The reader of  claim 21  wherein the hardware element is reconfigurable by the processor in real-time with the experienced condition.  
     
     
         25 . The reader of  claim 21  wherein the predetermined condition is the detection of a mixed tag population.  
     
     
         26 . The reader of  claim 25  wherein the mixed tag population includes two tags operating on differing protocols.  
     
     
         27 . The reader of  claim 26  wherein the protocols are at least one of a Class 0 specification, C1G1 specification, C1G2 protocol, ISO 18000-6a protocol, ISO 18000-6b protocol, 18000-6c protocol, and ISO15693 protocol.  
     
     
         28 . The reader of  claim 21  wherein the predetermined condition is an operating frequency of a tag.  
     
     
         29 . The reader of  claim 21  wherein the frequency of the tag is at least one of low frequency, high frequency, and ultrahigh frequency.  
     
     
         30 . The reader of  claim 21  wherein the frequency of the tag ranges from 860 MHz to 960 MHz.  
     
     
         31 . The reader of  claim 21  wherein a first antenna is configured to receive RF signals for a listen-before-talk reader and to transmit an interrogation signal.  
     
     
         32 . The reader of  claim 21  wherein the programmable processor is at least one of a digital signal processor, micro-controller, and general purpose processor.  
     
     
         33 . The reader of  claim 32  wherein a protocol is implemented by three computing cores, the three computing cores being the reconfigurable hardware element, a digital signal processor, and a general purpose processor.  
     
     
         34 . The reader of  claim 21  wherein the predetermined condition is a read rate of the reader over a time period.  
     
     
         35 . The reader of  claim 21  wherein the predetermined condition is determined from a first predictive model using a read rate during a first time period and a second predictive model using a read rate during a second time period, the second time period being relatively shorter than the first time period.  
     
     
         36 . The reader of  claim 35  wherein the second period is at least one of (i) less then 30 seconds, (ii) less than 15 seconds, and (iii) less than one second.  
     
     
         37 . The reader of  claim 36  wherein the time period is at least one of (i) longer than 5 minutes, (ii) longer than 10 minutes, and (iii) longer than 20 minutes.  
     
     
         38 . The reader of  claim 35  wherein the first time period includes the second time period.  
     
     
         39 . The reader of  claim 35  wherein the at least one reconfigurable hardware element alters a read rate of the reader based upon the predetermined condition.  
     
     
         40 . The reader of  claim 39  wherein the read rate of the reader can range from a predetermined minimum value to a predetermined maximum value.  
     
     
         41 . The reader of  claim 21  wherein the predetermined condition is a detected bearing of a tag.  
     
     
         42 . An RFID reader comprising: 
 a processor;    at least one antenna;    a switch controlled by the processor; and    at least two receiver channels coupled to the at least one antenna and the switch, the at least two receiver channels including: 
 a first receiver channel configured to provide a first gain for a received signal of a first predetermined range in strength, the first gain being substantially linear over the first predetermined range; and  
 a second receiver channel configured to provide a second gain for a received signal of a second predetermined signal range in strength, the second gain being substantially linear over the second predetermined range; and  
   at least one baseband receiver channel providing a third gain for a received signal after demodulation to a baseband.    
     
     
         43 . A method of operating an RFID system, the method comprising: 
 providing a tag population including first tags configured for a first communication protocol and second tags configured for a second communication protocol;    configuring a reader for communication using a first protocol;    commanding the first tags to an unresponsive state;    after the commanding, configuring the reader for communication using a second protocol; and    communicating by the reader with the second tags.    
     
     
         44 . The method of  claim 43  further comprising, after communicating by the reader with the second tags, reconfiguring the reader for communication using the first protocol and communicating by the reader with the first tags.  
     
     
         45 . The method of  claim 43  wherein the unresponsive state is a SLEEP state.